Modern automated bakeries typically employ track ovens for the baking of bread, buns, rolls, and other bakery products. In a track oven, a track extends through a bakery enclosure, and a drive chain extends through the track and supports spaced apart conveyor grids. The grids receive and transport bakery pans and trays.
In the operation of a track oven, dough products are received on the trays which are then loaded onto the grids of the track oven. The grids and the dough-laden trays carried thereby are transported through the oven enclosure which is heated by ribbon burners. Air circulation apparatus may be utilized within the oven enclosure to provide a more even temperature distribution therein. The length of the track conveyor and the speed of operation thereof are regulated so that baking of the dough products is completed during transportation thereof through the oven.
Track ovens typically comprise spiral configurations having elongated side portions to accommodate the ribbon burners. U.S. Pat. No. 4,726,766, granted to Stewart, et al. on Feb. 23, 1988, discloses a track oven having an inner ascending spiral and an outer descending spiral which allows both the conveyor inlet and the conveyor outlet to be at the level of the lowest conveyer tier. The '766 Patent also discloses an air circulation system that receives heated air from the upper region of the oven enclosure and discharges the heated air onto portions of the track conveyor that are physically separated from the ribbon burners.
The primary heating mechanism of track ovens utilizing ribbon burners is radiant heating from the burner flame. Radiant heating is notoriously inefficient as compared with the much more efficient heat transfer that can be achieved utilizing forced convection heating. However, it has not heretofore been possible to provide forced convection heating in track ovens due to the very large size of the conveyors and the surrounding oven enclosures which are required in order to provide the through-put rates required of modern bakeries.
The present invention comprises a forced convection track open oven which overcomes the foregoing and other problems that have long since characterized the prior art. In accordance with one aspect of the invention, a track oven is provided with a plurality of burners, each associated with a particular zone within the oven. The burners produce heated air that is discharged through a plurality of discharge tubes and an associated discharge nozzle. Fans are employed to circulate previously heated air through the burners, and the discharge tube/discharge nozzle structure functions to combine cooler used air with hot primary air for discharging into engagement with the bakery pans that are transported by the track conveyor.
In accordance with another aspect of the invention, the track conveyor comprises two circular spirals, one ascending and one descending. The use of circular spirals is advantageous is reducing the likelihood of pan jamming that has characterized prior track oven designs. Perhaps more importantly, the use of the circular spiral configuration in combination with discharge tubes and discharge nozzles to effect heating allows the use of distinct zones within the oven, thereby affording better control over the baking process.
In accordance with yet another aspect of the invention, the track conveyor comprises two oval spirals, one ascending and one descending. The use of oval spirals is advantageous in those circumstances in which the required conveyor track length cannot be accommodated using circular spirals due to reduced ceiling height. In such circumstances the use of oval spirals is advantageous in providing extended track length in a reduced height environment.